1. Field of the Invention
The present invention relates to a pharmaceutical preparation containing a vasoactive intestinal polypeptide (hereinafter referred to as "VIP") or its analogue and more particularly, to a preparation excellent in absorptiveness.
2. Related Arts
The VIP is one of the peptide hormones and was first isolated and refined by Said and Mutt in the year of 1970 from a subfraction, when secretin was extracted from a tissue of porcine upper small intestine. In 1974, a primary amino acid structure of the VIP was made apparent as consisting of 28 amino acids and it has been considered that it belongs to a glucagon-secretin family.
Amino acid sequence of the native VIP (SEQ ID NO: 1) ##STR1##
It has been confirmed that the VIP is present in nervous systems in addition to the digestive canal to develop various biological activities, for instance a relatively high vasodilating-hypotensing action; atonic action on smooth muscle; accelerating action of intestinal juice secretion, pancreatic juice and bile secretions, and tear secretion; suppressing action of gastric juice secretion; accelerating action of glycogen decomposition; accelerating action of various pituitary hormone secretions; increasing action of blood flow into penis; vasodilating action of bronchus; anti-allergic action; anti-tumor action; growing action of hair, and so on.
Following patent literatures have been issued in Japan on the VIP, VIP analogues and use thereof.
a) Jap. Pat. No. Sho 56 (Year of 1982)--128721(A), Anti-allergic agent; PA0 b) Jap. Pat. No. Sho 62 (Year of 1987)--16429(A), Acceleration of tear secretion; PA0 c) Jap. Pat. No. Sho 62 (Year of 1987)--116595(A), Anti-tumor and ulcer agent; PA0 d) Jap. Pat. No. Sho 62 (Year of 1987)--246595(A), Bronchodilatation agent and hypotensor; PA0 e) Jap. Pat. No. Sho 63 (Year of 1988)--179892(A), Acceleration of blood flow; PA0 f) Jap. Pat. No. Sho 64 (Year of 1989)--83012(A), An agent for growing hairs; PA0 g) Jap. Pat. No. Hei 1 (Year of 1989)--296996(A), Hypotensor; and PA0 h) Jap. Pat. No. Hei 2 (Year of 1990)--76821(A), External preparation for curing impotence.
In view of those biological activities, the VIP has been expected as the drugs for curing asthma and impotence, by utilizing the bronchodilitating and atonic activities on smooth muscle of corpus cavernosum, respectively. A structural characteristic of the VIP lies in that there is an amide structure at the C-terminal, which has been estimated as an indispensable matter for developing the biological activities of VIP.
Hitherto, it has been considered as quite difficult to provide the VIP or VIP analogues with a reasonable price and in a large amount, since according to the prior arts, there is no way other than utilizing a synthetic process therefor or an extraction method thereof from an animal tissue, and the former requires troublesome operations due to that the VIP is polypeptide consisting of 28 amino acids, and takes a relatively long period of time in its chemical synthesis and for purifying the same, and the latter is restricted on availability of the raw material and requires troublesome purification procedures.
For obtaining a polypeptide having an amide structure at C-terminal as the VIP in accordance with conventional and widely accepted biological techniques which utilize an expression microorganism such as Escherichia coli, in general, it is required to separate and purify an expressed polypeptide and then to treat the polypeptide with use of a special C-terminal amidation enzyme. However, such an enzymatic method is not suitable for industrial scale production, since such enzyme is expensive and yield of the objective polypeptide becomes low.
It has also been reported that a chemically synthesized VIP analogue--methionine residue at 17th position of the native type VIP being substituted with leucine or norleucine--shows biological activities similar to the native type VIP [said Jap. Pat. No. Sho 62 (Year of 1987)--246595(A)]. Therefore, it has been considered that the methionine residue at 17th position has almost no influence on useful activities of the VIP.
The present inventors have energetically studied and investigated polypeptides obtained through a fermentation method or chemical synthesis and with a VIP-like structure to find out that a polypeptide represented by a following formula and obtained through the cleaving step using cyanogen bromide shows desired biological activities in same level or higher than native type VIP and [Leu.sup.17 ]-VIP, and that an amide or alkyl amine can easily be bound to the residue in accordance with a conventional synthetic method, to open a way for producing the VIP analogues in a large amount and with a reasonable cost [Jap. Pat. Appln. Nos. Hei 2 (Year of 1990)--165739 and 408425 which correspond to U.S. Ser. No. 07/704,143 and EP-0 463 450(A1) (SEQ ID NO: 2): EQU His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Thr-Arg-Leu-Arg-Lys-Gln-X-Ala-Val-L ys-Lys-Tyr-Leu-Asn-Ser-Ile-Leu-Asn-Y
wherein X is a residue of amino acid other than methionine (Met); and Y is homoserine, homoserine-lactone, amidized homoserine, a residue reacted homoserine-lactone with a primary alkyl amine having carbon atoms not exceeding 20, or an optional polypeptide chain and containing an amidized homoserine at C-terminal.
In general, biologically active peptides are apt to be affected by external factors such as heat, humidity, light beam and peptidase. Therefore, the inventors have checked the stability thereof and groped for various methods for administration thereof for developing an actual medicine comprising the VIP analogue as an effective ingredient and found out that the VIP analogues are somewhat improved in stability than the native type VIP and [Leu.sup.17 ]-VIP, but can not be said as having a sufficient stability. Namely, if the VIP analogue is dissolved in water to lyophilize the solution and the resulting powder is stored in a refrigerator and the powder is dissolved into saline or the like, when the time for administration by injection, a reduction of activity can be fairly suppressed, but the injection accompanies a pain to patients to restrict an application range, and in other administration methods such as oral dosage, suppository or the like, the VIP analogue is apt to be decomposed and lack a development of expected pharmacological activity.